The present invention relates to a permanent anti-static polycarbonate resin composition. More particularly, the present invention relates to a resin composition having excellent heat and impact resistances and also a drastically improved anti-static property, and a resin composition having heat and impact resistances, an improved anti-static property and also a phenomenally improved weld strength. Owing to its excellent anti-static property, the resin composition of the present invention is usefully applicable to the fields of electric and electronic equipment and precision machinery where durability of anti-static quality is required.
Generally, synthetic polymers have high electric resistivity and are easily charged by a friction such as rubbing, or exfoliation to collect dust and foreign particles, thereby spoiling the appearance of their molded products. Further, in the field of electric and electronic devices composed of these polymers, there often arise troubles causing in such static charging of the polymers. Development of a new polymeric material having an excellent permanent anti-static property has been desired.
Many studies have been performed for endowing anti-static property to the synthetic resin-made articles. Typically, it is known to apply a surfactant-based type anti-static agent on the fabricated article or blend an anti-static agent in the resin material for affording the anti-static property to the article.
The resin composition obtained by these process, however, has a defect that the antistatic agent in the surface layer of the article would be lost in long-time use. The antistatic property would also be lowered with frictional wear of the surface layer.
Regarding polycarbonate resin compositions having anti-static property, Japanese Patent Application laid-open (KOKAI) No. 62-273252 proposes a resin composition comprising a polyether ester amide composed of 10 to 95% of polyether ester units in the whole units and a polycarbonate resin.
Also, Japanese Patent Application laid-open (KOKAI) No. 1-163252 proposes a four-component resin composition consisting of (1) a polyether ester amide composed of 10 to 90 wt % of polyether ester units, (2) a polycarbonate resin, (3) a modified vinyl polymer and a rubber-like polymer and (4) a graft copolymer obtained by graft polymerizing an aromatic vinyl monomer, an acrylic or methacrylic ester monomer or a vinyl cyanide monomer.
Further, Japanese Patent Application laid-open (KOKAI) No. 7-26131 proposes a resin composition consisting of an aromatic polycarbonate, a polyamide-polyether block copolymer, a phosphite-based compound and a core-shell type graft rubber-like elastomer.
The resin compositions disclosed in the above references all show good impact resistance, heat resistance and anti-static property. However, there is no description on weld strength of the compositions in these references. Accordingly, in these references, there is no discussion on durability against frictional wear, nor any consideration to the retention of anti-static property in long-time use.
The present inventors have also pursued studies on the subject matter for a resin composition having permanent anti-static property. In Japanese Patent Application laid-open (KOKAI) No. 7-224217, the present inventors proposed a permanent anti-static resin composition having improved heat stability obtained by adding a compound having a spiro ring structure to polycarbonate, polyester and block copolyamide resins.
The permanent anti-static resin compositions proposed above, although capable of improving anti-static property of the articles to a certain extent, may cause the impairment of the appearance of the polycarbonate resin molded articles and also tend to cause an excessive reduction of strength of the weld portion, for which the block copolyamide resin is responsible, so that these resin compositions are still unsatisfactory for the long-time stable retention of the high-level anti-static quality of the articles.
Thus, there has yet been available no resin composition which can satisfy all of the quality requirement such as improved anti-static property, excellent heat resistance, excellent impact resistance, good appearance of the molded article and excellent weld strength in a well-balanced manner.
As the result of the present inventor's earnest studies and researches on the subject matter, it has been found that by blending an aromatic polycarbonate resin, a block copolyamide resin, an aromatic polyester resin, a specific multi-layered polymer and a phosphorus compound having a spiro ring structure at the specified ratios, the obtained resin composition is drastically improved in anti-static property, can maintain excellent static charge controlling performance even in long-time use, can inhibit the impairment of appearance of the molded article, has an excellent impact resistance, suffers little reduction of heat resistance in use and is greatly improved in weld strength. The present invention has been attained on the basis of the above finding.